I love this idea, just needs to be implemented right. In my experience ideas last for maybe week or so before everything falls apart. Someone done with their couple week binge of a game? IRL issues? Power player who wants to progress faster and have everything done ASAP? Things to consider
A lot of games are classified as SMP, (survival multiplayer) and for the reason you described above I think of them more as MSP (Multi single player) because people always run off.
I hope this idea works and I would be interested in it. Could even do some fun mods to add classes and gear to help flesh out roles. Though there might be the thing of someone's role falling by the wayside or not enjoying it as much.